Continuous x-ray fluorescent analysis of the solid component of a slurry



May 6, 1969 K. G. CARR-BRION ETAL 3,443,092

CONTINUOUS X-RAY FLUORESCENT ANALYSIS OF THE SOLID COMPONENT OF A SLURRY Filed June 16, 1966 Sheet of 2 [RSZZZ 700- e mang I I I 1 y 1969 K.G. CARR-BRION ETAL 3,443,092

CONTINUOUS X-RAY FLUORESCENT ANALYSIS OF THE SOLID COMPONENT OF A SLURRY Filed June 16, 1966 Sheet 3 of 2 AMPL/F/EP 504(6)? T/MER A ttorneyg United States Patent US. Cl. 250-515 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for testing continuously the concentration of a given element in the solid component of a slurry in which the solid component is at least partially separated centrifugally from the slurry, the solid component so separated being moved in a continuous layer across and in contact with a window of said apparatus,

and the solid component in said layer being analyzed by means of radiation transmitted through said window.

This invention comprises improvements in or relating to the continuous analysis of the solid component of a slurry. The handling of solids in many manufacturing processes is assisted by suspending the solids in a liquid slurry. Where it is desired to perform a continuous analysis of the solids in the slurry as a way of, for example, monitoring some stage of a manufacturing process to control the same, some arrangement for presenting the solid component of the slurry independently of the liquid component is desirable. This is particularly true, for example, where the analysis of the solid component is performed by an X-ray fluorescence technique, since the result of the analysis must otherwise be corrected for the concentration of the solids in the slurry, a correction which requires a precise knowledge of the density of the slurry and the solid component, which is in many cases diflicult to obtain.

The present invention provides, in one aspect, a method of testing continuously the concentration of a given element in the solid component of a slurry in which the solid component is at least partially separated centrifugally from the slurry, the solid component so separated is moved in a continuous layer across and in contact with a window, and the solid component in said layer is analysed by means of radiation transmitted through said window.

Preferably said analysis is effected by inducing X-ray fluorescence of the solid component in said layer and analysing the said fluorescence X-rays transmitted through said window.

The invention provides, in another broad aspect, apparatus for continuously presenting the solid component of a slurry for analysis comprising a cylindrical chamber having slurry inlet and outlet means, means for causing at least partial centrifugal separation of the solid component from the slurry, a window located in an end wall of the chamber so that in operation of the apparatus at least some of said solid component which has been separated from the slurry moves across the window in a continuous layer in contact therewith and slurry outlet means located axially in the chamber adjacent said window.

Preferably said outlet means comprise a conduit communicating with the interior of the chamber at an orifice provided centrally in a baflle member extending parallel to and spaced from the surface of the window. The spacing between the baflle member and the surface of the window is preferably adjustable.

The internal surface of the window may be coated, at least over the central portion thereof, with an abrasion resistant layer of synthetic resin material.

According to a preferred embodiment the means for causing centrifugal separation of the solid component, and said slurry inlet means, comprise an inlet pipe extending tangentially to the curved surface of the cylinder in a plane perpendicular to the axis thereof. fil Preferably the window is formed of a synthetic resin Preferably the window is supported in the chamber wall -by a retaining member which is sealingly engaged with said wall and which has a film-engaging portion whereby movement of the retaining member relative to the chamber wall adjusts the tension in the film.

The preferred application of the apparatus referred to above is to the analysis of the solid component of a slurry by X-ray fluorescence. According, therefore, to another aspect of this invention, there is provided apparatus for testing continuously the concentration of a given element in the solid component of a slurry comprising apparatus for presenting the solid component for analysis as herein before defined in combination with analysing means for analysing radiation transmitted through the window. In a preferred embodiment, the apparatus includes means for inducing X-ray fluorescence of the solid component in said layer, said analysing means comprising means for analysing said X-ray fluorescence.

Preferably the analysing means is responsive to a predetermined component of the characteristic X-radiation of the iven element.

Said means for inducing X-ray fluorescence are preferably located externally of said window and comprise an X-ray tube or a radioactive source of X-rays.

Means are preferably provided for adjusting the rate of flow of slurry through the chamber.

A purely exemplary description of the invention will be given with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic sectional view through apparatus for continuously presenting the solid component of a slurry for analysis constructed and arranged in accordance with the invention;

FIGURE 2 is a graphical representation of the effect of an X-ray fluorescence analysis of the concentration of the solid component in a slurry, and

FIGURE 3 is a diagrammatic view, partly in section, of X-ray fluorescence analysis apparatus employing the invention.

Referring to FIGURE 1 the apparatus comprises a cylindrical chamber 10 formed of duralumin which is closed at one end by a plane wall 11 and which is open at the other end. The chamber 10 is bounded at its open end by a continuous radially extending flange 12 having a bevelled surface 12a at the entrance to the chamber 10.

The open end of the cylindrical chamber 10 is closed by a thin window 13 which extends over the flange 12 and is held in contact with the surface of the flange 12 by an annular duralumin retaining member 14. The radially inner portion of the member 14 is formed with a continuous raised lip 15, which is disposed parallel to the bevelled surface 12a of the flange 12. The retaining member '14 is adjustable relatively towards or away from the flange 12 by means of screws 16 which pass through the member 14 and are received in threaded apertures in the flange 12. The position of the retaining member 14 relative to the flange 12 determines the tension in the window 13. The joint between the flange 12 and the retaining member 14 is rendered fluid tight by means of an annular rubber gasket 17.

The chamber 10 is provided adjacent the end wall 11 with a slurry inlet pipe 18 which extends tangentially to the cylindrical surface of the chamber in a plane perpendicular to the axis thereof. Means (not shown) are provided for pumping slurry into the chamber through the inlet pipe 18 at an adjustable rate.

Slurry outlet means are provided in the form of an outlet pipe 19 extending axially of the cylindrical chamber 10 and terminating in the chamber 10 at an orifice 20 provided centrally of a disc-like plane baffle member 21. The baffle member 21, which in the illustrated embodiment is formed as a continuous flange at the end of the outlet pipe 19, extends parallel to and is spaced a short distance from the surface of the window 13. The outlet pipe 19 passes in screw-threaded engagement through a brass bush 22 which is fluid-tightly mounted in an aperture centrally of the end wall 11. The spacing between the baflle member 21 and the surface of the window 13 is adjustable by screwing the outlet pipe 19 into or out of the chamber 10 as necessary.

The window 13 is formed of polyester film, such as that known by the trade name Melinex, supported by a nylon mesh. The tension in the film is adjusted by suitable setting of the screws 16. The thickness of the window varies according to the penetrating power of the characteristic X-rays being measured, a typical thickness being 0.005 inch. To protect the window 13 from abrasion by the slurry the central portion of the surface of the window 13 opposite the orifice 20 is provided with a protective layer 23 such as, for example, a layer 0.1 to 0.2 mm. thick of impact adhesive.

In operation of the apparatus, slurry entering the chamber 10 through the tangential inlet 'pipe 18 has imparted to it a vortex flow which induces at least partial centrifugal separation of the solid component from the slurry, said solid component being forced centrifugally against the cylindrical walls of the chamber 10. The slurry flows between the walls of the chamber 10 and the bafile member 21, leaving the chamber through the orifice 20 and the outlet pipe 19. The said solid component which has been separated from the slurry passes continuously along a vortex path from the cylindrical wall of the chamber 10 radially inwardly towards the axis of the chamber 10 in a continuous layer in contact with the window 13. As a result, the solid component of the slurry is presented to the window 13 as a continuous close packed layer, so that analysis of said solid component may be made independently of the remainder of the slurry and measurements can be made without having to take into account the concentration of the solid component in the slurry.

This is illustrated by the particular application of the invention to continuous on stream analysis of a slurry by the X-ray fluorescence technique. This technique, which is described, for example, in U.K.A.E.A. Research Group Report AERE-R4474, is applicable to the determination of the concentration of a given element in the solid component of a slurry. Such a determination has previously necessitated a knowledge of the concentration of the solid component in the slurry, which in many cases is difficult to obtain. If, however, the slurry is presented for analysis by passing it through apparatus such as that in FIGURE 1, then the layer of solid component which forms at the window 13 can be analysed independently of the remainder of the slurry.

The X-ray fluorescence analysis apparatus illustrated schematically in FIGURE 3 includes a slurry presenting chamber 10 in accordance with the invention. The slurry to be analysed is circulated through the chamber 10, in the manner described above, in a closed circuit including a peristaltic pump 25 and a reservoir 26. A stirrer 27 is disposed in the reservoir 26.

A radioactive point source 30 (FIGURE 3) emitting X-rays is mounted externally of the window 13 of the presenter chamber 10. The source 30 is so selected that the X-rays emitted thereby cause X-ray fluorescence of the solid component of the slurry in the layer behind the window 13. The X-ray fluorescence passes out through the window 13 and is analysed using a detecting system. The detecting system, shown diagrammatically, comprises a scintillation counter 32 which is rendered responsive to a predetermined characteristic X-radiation of the given element by the interposition of suitable filters 33. The intensity of the fluorescence is indicated by a sealer-time unit 34 connected to the scintillation counter 32 through an amplifier 35 and pulse height analyser 36. The fluorescence intensity will be a function of the concentration of the given element in the solid component of the slurry, independently of the concentration of the solid component in the slurry, provided the depth of the layer formed at the window 13 exceeds a critical depth equal to the depth of the solid component from which the characteristic X-rays detected by the detecting system originate. The spacing between the baflle member 21 and the window 13 is adjusted to a value in accordance with the physical characteristics of the slurry under analysis.

FIGURE 2 illustrates graphically an analysis of a slurry the solid component of which contains barium. The variation of the fluorescent X-ray intensity of barium Ka characteristic radiation is plotted as a function of the concentration in a slurry of the solid component, using the apparatus for presenting the solid component according to the invention. The X-ray intensity is indicated as the count rate per second of a proportional counter which is responsive to the barium Ka radiation, the concentration of the solid component or solid content of the slurry being expressed as a percentage by Weight. It is seen that, above about 1% solid component concentration, the intensity measured is substantially independent of the solid content of the slurry, illustrating the effectiveness of the apparatus in separating the solid component and presenting it for analysis.

We claim:

1. A method of testing continuously the concentration of a given element in the solid component of a slurry comprising the steps of:

partially centrifugally separating a solid component from the slurry;

moving the solid component so separated in a continuous layer across and in contact with a window; and analyzing the solid component in said layer by means of radiation transmitted through said window.

2. A method as claimed in claim 1 wherein said step of analyzing includes the steps of:

inducing X-ray fluorescence of the solid component in said layer; and

analyzing the said fluorescence X-rays transmitted through said window.

3. Apparatus for continuously presenting the solid component of a slurry for analysis comprising a cylindrical chamber having slurry inlet means, means in said chamber for causing at least partial centrifugal separation of the solid component from the slurry, a window located in an end wall of the chamber and slurry outlet means located axially in the chamber adjacent said window, whereby in operation at least some of said solid component which has been separated from the slurry moves across the window in a continuous layer in contact therewith before leaving via the outlet means.

4. Apparatus as claimed in claim 3 wherein said outlet means comprise a conduit extending centrally into the chamber and a baffle member disposed parallel to and spaced from the surface of the Window.

5. Apparatus as claimed in claim 4 including means for adjusting the spacing between the baflle member and the surface of the window.

6. Apparatus as claimed in claim 3 wherein the internal surface of the window is coated, at least over the central portion thereof, with an abrasion-resistant layer of synthetic resin material.

7. Apparatus as claimed in claim 3 wherein the means for causing centrifugal separation of the solid component,

and said slurry inlet means, comprise an inlet pipe extending tangentially to the curved surface of the cylindrical chamber in a plane perpendicular to the axis thereof.

8.,Apparatus as claimed in claim 3 wherein the window is formed of a synthetic resin film.

9. Apparatus as claimed in claim 8 wherein a retaining member supports the window in the chamber wall, said retaining member being sealingly engaged with said wall and having a film-engaging portion whereby movement of the retaining member relative to the chamber wall adjusts the tension in the film.

10. Apparatus as claimed in claim 8 wherein said film is a polyester film.

11. Apparatus for testing continuously the concentration of a given element in the solid component of a slurry comprising apparatus for presenting the solid component for analysis as claimed in claim 3 in combination with analysing means for analysing radiation transmitted through the window.

12. Apparatus as claimed in claim 11 including means for inducing X-ray fluorescence of the solid component in said layer, said analysing means comprising means for analysing said X-ray fluorescence.

13. Apparatus as claimed in claim 12 wherein the analysing means is responsive to a predetermined component of the characteristic X-radiation of the given element.

14. Apparatus as claimed in claim 12 wherein the means for inducing X-ray fluorescence are located externally of said window and comprise a source of X-rays.

15. Apparatus as claimed in claim 11 including means for adjusting the rate of flow of slurry through the chamber.

References Cited UNITED STATES PATENTS 3,150,261 9/1964 Furbee et al. 250-515 3,259,743 7/1966 Pick et al 25051.5 3,354,308 11/1967 Engel et al. 25051.5

RALPH G. NILSON, Primary Examiner. A. L. BIRCH, Assistant Examiner.

US. Cl. X.R. 250-435 

